Orthogonal frequency division multiplexing (OFDM) is a popular multicarrier modulation method that has been adopted in numerous standards such as IEEE 802.11a/g, DVB-T/T2, and LTE. Some of the key advantages of OFDM are its high spectral efficiency, robustness to inter-symbol interference (ISI) caused by multipath, and its ability to equalize wideband channels. However, OFDM is sensitive to time and frequency offsets, which need to be estimated in order to correctly demodulate the received data.
Some techniques focus on blindly estimating these offsets without the use of training data. Typically, the maximum likelihood (ML) principle has been used in these approaches because it guarantees asymptotically unbiased and consistent estimates. However, the mutual orthogonality of the OFDM subcarriers is preserved only if the estimated timing error lies in the lock-in region. The previously proposed estimators have been designed to accurately estimate the symbol time offset (STO), but not necessarily designed to lock-in with high probability.